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package org.openjdk.jmh.samples;


import org.openjdk.jmh.annotations.Benchmark;

import org.openjdk.jmh.annotations.BenchmarkMode;

import org.openjdk.jmh.annotations.Fork;

import org.openjdk.jmh.annotations.Measurement;

import org.openjdk.jmh.annotations.Mode;

import org.openjdk.jmh.annotations.OutputTimeUnit;

import org.openjdk.jmh.annotations.Scope;

import org.openjdk.jmh.annotations.Setup;

import org.openjdk.jmh.annotations.State;

import org.openjdk.jmh.annotations.Warmup;

import org.openjdk.jmh.infra.Blackhole;

import org.openjdk.jmh.runner.Runner;

import org.openjdk.jmh.runner.RunnerException;

import org.openjdk.jmh.runner.options.Options;

import org.openjdk.jmh.runner.options.OptionsBuilder;


import java.util.concurrent.TimeUnit;


@BenchmarkMode(Mode.AverageTime)

@OutputTimeUnit(TimeUnit.NANOSECONDS)

@Warmup(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)

@Measurement(iterations = 5, time = 1, timeUnit = TimeUnit.SECONDS)

@Fork(1)

@State(Scope.Thread)

public class JMHSample_28_BlackholeHelpers {


 /**

  * Sometimes you need the black hole not in @Benchmark method, but in

  * helper methods, because you want to pass it through to the concrete

  * implementation which is instantiated in helper methods. In this case,

  * you can request the black hole straight in the helper method signature.

  * This applies to both @Setup and @TearDown methods, and also to other

  * JMH infrastructure objects, like Control.

  *

  * Below is the variant of {@link org.openjdk.jmh.samples.JMHSample_08_DeadCode}

  * test, but wrapped in the anonymous classes.

  */


 public interface Worker {

  void work();

 }


 private Worker workerBaseline;

 private Worker workerRight;

 private Worker workerWrong;


 @Setup

 public void setup(final Blackhole bh) {

  workerBaseline = new Worker() {

   double x;


   @Override

   public void work() {

    // do nothing

   }

  };


  workerWrong = new Worker() {

   double x;


   @Override

   public void work() {

    Math.log(x);

   }

  };


  workerRight = new Worker() {

   double x;


   @Override

   public void work() {

    bh.consume(Math.log(x));

   }

  };


 }


 @Benchmark

 public void baseline() {

  workerBaseline.work();

 }


 @Benchmark

 public void measureWrong() {

  workerWrong.work();

 }


 @Benchmark

 public void measureRight() {

  workerRight.work();

 }


 /*

  * ============================== HOW TO RUN THIS TEST: ====================================

  *

  * You will see measureWrong() running on-par with baseline().

  * Both measureRight() are measuring twice the baseline, so the logs are intact.

  *

  * You can run this test:

  *

  * a) Via the command line:

  *    $ mvn clean install

  *    $ java -jar target/benchmarks.jar JMHSample_28

  *

  * b) Via the Java API:

  *    (see the JMH homepage for possible caveats when running from IDE:

  *      http://openjdk.java.net/projects/code-tools/jmh/)

  */


 public static void main(String[] args) throws RunnerException {

  Options opt = new OptionsBuilder()

          .include(JMHSample_28_BlackholeHelpers.class.getSimpleName())

          .build();


  new Runner(opt).run();

 }
// 本例介绍了 Blackhole 不仅可以用在 Benchmark 修饰的方法上，也可以用在其他JMH提供的方法上，比如 @Setup 和 @TearDown 等等

}

